1. Field of the Invention
The present invention relates to a Multiple Input Multiple Output (MIMO) wireless communication system. More particularly, the present invention relates to an apparatus and method for supporting both a receiver using a single antenna and a receiver using multiple antennas in a MIMO wireless communication system.
2. Description of the Related Art
Recently, with the growing demand for high quality TeleVision (TV) services, much attention is being paid to digital TV broadcasting. One benefit of Digital TV broadcasting is its provision of a higher definition image as compared with conventional analog TV broadcasting. Digital TV broadcasting is classified into Standard Definition (SD) broadcasting and High Definition (HD) broadcasting according to image resolution. Since HD broadcasting provides a high quality TV service having a higher resolution than that of the SD broadcasting, a greater channel capacity is required to provide the HD broadcast. Therefore, in order to provide HD broadcasting using a limited frequency resource, a Multiple Input Multiple Output (MIMO) technique has been considered. That is, by using a plurality of Transmit (Tx) antennas, a broadcasting system can secure the channel capacity required for HD broadcasting.
A receiver having a plurality of Receive (Rx) antennas can receive an HD broadcast that employs the MIMO technique. However, when a receiver having only a single Rx antenna, designed in consideration of only the conventional SD broadcasting, desires to receive an HD broadcast, an antenna for receiving the HD broadcast has to be additionally installed in the receiver. Furthermore, when a transmitter transmits both the SD broadcast signal and the HD broadcast signal by using a Spatial Multiplexing (SM) scheme, which is a MIMO technique, the receiver having the single antenna cannot receive even the SD broadcast.
When a plurality of Rx antennas are provided to receive an HD broadcast signal, successful reception of the HD broadcast signal depends on locations of the antennas. When the Rx antennas are located indoors, it may be difficult to ensure a minimum antenna spacing which is required to use the SM scheme. Further, when the Rx antennas are located indoors, reliability of signal reception may deteriorate due to a low Rx signal strength. On the other hand, when the Rx antennas are located outdoors, an additional cable must be installed to provide a signal path between a receiving device and an antenna. Further, when the Rx antennas are located outdoors, a Line Of Sight (LOS) environment is formed among the Rx antennas, which makes it difficult to obtain a spatial multiplexing gain.
As described above, when the MIMO technique is used for HD broadcasting, there is a problem in that a receiver, which uses the conventional SD broadcasting service and has a single antenna, cannot receive a broadcast signal. In addition, a receiver, which has a plurality of antennas in order to use the HD broadcast service, may not obtain a spatial multiplexing gain depending on an antenna environment. Furthermore, the same problem may occur when the MIMO technique is applied to a communication system in which two or more signals each having differentiated throughput co-exist, similar to a relationship between the SD broadcast signal and the HD broadcast signal in the digital TV broadcast.